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RF Electronics Chapter 5: Frequency Mixers Page 143 2022, C. J. Kikkert, James Cook University, ISBN 978-0-6486803-9-0. Figure 5.52 shows a comparison between the spectra of the DBM, TBM and HL-DBM used as up-converters. The relationship between the spectral components and LO and RF frequencies are shown in table 5.1. For the TBM and HL-DBM the spectra are near ideal, with the largest unwanted components being 76.9 dB below the wanted components. For the DBM the largest unwanted components are 63.3 dB below the wanted components. Comparing the TBM or HL-DBM performance in figure 5.52 with the DBM performance in figures 5.52 and 5.38 and with the Balanced Mixer performance in figure 5.29, shows that the TBM or HL-DBM should be used in applications where superior performance is required. During computer simulation the LO-RF and the RF-LO isolation is ideal. In practice that is not the case, since firstly the diodes will not be matched exactly and secondly there will be slight differences in capacitive coupling between the different windings in the transformers. As a result, the typical isolation and conversion loss of practical mixers is worse than the computer simulations. Table 5.3 compares 3 different types of mixers, from the same manufacturer, all made using core and wire technology. The performance data is taken from the data sheets for an RF signal at or close to 2.5 GHz. Computer simulation result in the same performance for TBM and HL-DBM devices. Table 5.3 shows that a better performance is achieved from TBM hardware. Table 5.3 Typical Mixer performance for a 2.5 GHz RF input [6-8]. MCA-35MH+ ADE-30W+ ADE-R30WLH+ Type TBM DBM High Rel DBM LO/RF 500-3500 MHz 300-4000 MHz 300-4000 MHz LO 13 dBm 7 dBm 10 dBm Conversion loss 5.95 dB 6.79 dB 8.21 dB LO-IF isolation 26.01 dB 12.0 dB 13.46 dB LO-RF isolation 30.44 dB 33.67 dB 40.68 dB IIP3 20 dBm 12 dBm 15 dBm Microwave Mixers At microwave frequencies (>1 GHz) transformers become progressively more difficult to make. In addition, the capacitance associated with the diodes used in the mixer cause the diodes to become less efficient as a mixer, any PCB's have larger skin depth and dielectric losses and ferrites have larger magnetic material losses. As a result, mixers at microwave frequencies have higher conversion losses than mixers used at lower frequencies. Conversion losses of 6 to 10 dB are typical. The frequency dependence of the conversion loss on the RF frequency can easily be seen from [2], selecting surface mount and level 7 devices and then sorting the devices according to frequency. The ADE-6+, core & wire based mixer with a 250 MHz upper frequency has a conversion loss of 4.6 dB, the 15 GHz upper frequency SIM-153+, LTCC based mixer has a conversion loss of 8 dB and the ZX05153-S+ core & wire based mixer has a conversion loss of 7.5 dB. Surface Mount Double balanced mixers are available to 40 GHz [9]. Balanced based mixers are available for frequencies up to 90 GHz [10]. RF Electronics: Design and Simulation 143 www.cadence.com/go/awr

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